A Gas Chromatograph (GC) detector comprises a first amplifier circuit (302(1)), a second amplifier circuit (302(2)), a digital subtractor (320) and a digital logic (325) to provide a GC measurement signal (330) in a digital form. Said first circuit (302(1)) includes a reference amplifier (332) comprising a first resistive bridge (337(1)), a first counter circuitry (305(1)) to provide a first counter output (317(1))). Said second circuit (302(2)) includes an amplifier (342) comprising a second resistive bridge (317(2)), a second counter circuitry (305(2)) to provide a second counter output (317(2)). Said digital subtractor (320) subtracts the first counter output (317(1)) from the second counter output (317(2)) and provides a digital subtractor output (322). Said digital logic (325) shared between one to many detector channels to implement at least a portion of the first counter circuitry and the second counter circuitry is arranged to receive the digital subtractor output (322) and provides the GC measurement signal (330). The GC detector (300) may be based on a Thermal Conductivity Detectors (TCD) (335(1),(335(2)) in which an analog difference amplifier and an integrator of a Sigma-Delta (Σ-Δ) A/D converter are eliminated and the Σ factor of the Sigma-Delta (Σ-Δ) A/D converter is accomplished in a digital form.